Our invention relates to apparatus for moving objects with precision over very small distances. The prior art of which we are aware teaches two basic types of such devices, herein referred to as "micropositioners." The first is a wholly mechanical arrangement in which screw threads and the like are used to translate the relatively gross motion of an operator's hand into a much smaller movement, or displacement, of the object to be moved. Disadvantageously, there is a limit to the precision with which mechanical parts can be machined. This, in turn, limits the precision to which displacements can be achieved (without resort to complex mechanical structures), typical displacement resolution being 2-5 microns.
Other micropositioners exploit in a straightforward way the fact that piezoelectric materials, for example, undergo a change in physical dimension when a voltage is impressed across them. Advantageously, these relatively simple devices can provide much more precise displacements than simple mechanical arrangements, typical displacement resolution being 0.001 microns. They have a number of drawbacks, however. Their maximum displacement is in the 10 micron range, which is insufficient for many applications, and which is achieved only by using very high voltages--a further disadvantage. Moreover, displacement as a function of applied voltage may be (a) nonlinear and (b) unstable over time. These factors make difficult precise control over, and readout of, the displacement. A further disadvantage is that the piezoelectric devices require a continuously applied voltage in order to maintain the displacement.